The present application Protein-protein interaction inhibitors as novel analgesics addresses the critical need for efficacious analgesics lacking adverse side-effects. The NMDA receptor is involved in the maintenance of chronic pain and other pathological neuronal diseases. Dr. Lai, a co-principal investigator for this project, first showed that the small molecule inhibitor IC87201 disrupts the functional protein-protein interaction involving PDZ domains (neuronal nitric oxide synthase, nNOS and postsynaptic density protein 95, PSD95) required for NMDA receptor signaling. IC87201 also attenuated hyperalgesia in a rat model of neuropathic pain produced by traumatic nerve injury. However, whether nNOS-PSD95 inhibitors suppress nociceptive processing remains unknown. The objective of this application is to validate disruptors of nNOS-PSD95 protein-protein interactions as broad spectrum analgesics that suppress nociceptive processing using animal models of evoked and spontaneous pain. Persistent pain associated with central nervous system sensitization will be produced using inflammatory and toxic neuropathic insults. IC87201, one of the first small molecule protein-protein interaction disruptors, shows efficacy in several preclinical pain models. These findings support our hypothesis that disruption of signal compartmentalization represents an innovative approach to develop novel analgesics with fewer side-effects. The investigators, with extensive combined experience in drug discovery (Lai) and development of novel pain models (Hohmann) are well-positioned to conduct the proposed work. We will conduct experiments proposed under two Specific Aims: (1) To evaluate antinociceptive efficacy of small molecule inhibitors of nNOS-PSD95 on both inflammation-evoked behavioral hypersensitivities and neuronal activation; (2) To assess the efficacy of small molecule inhibitors of nNOS-PSD95 in suppressing spontaneous neuropathic pain using a conditioned place preference approach. Completion of this project is expected to validate the use of nNOS-PSD95 inhibitors as a new class of broad-spectrum analgesics. These studies are expected to validate the disruption of signal compartmentation as an innovative and feasible approach to drug development. The development of effective pharmacotherapies with novel chemical structures that possess limited side-effect profiles and minimal abuse liability is expected to drive down health care costs and alleviate suffering in patients.